In the field of toners for electrophotography, it has been demanded to develop toners having a smaller particle size and an excellent fusing ability in view of achieving higher image qualities. Conventional processes for producing the toners include a melt-kneading and pulverization method, and a wet process such as an emulsification and aggregation method. In these methods, binder resins, for example, those composed mainly of a polyester, are used to obtain toner particles from the viewpoint of a good fusing ability thereof.
Conventionally, in some kinds of polyesters as the binder resin, a trivalent carboxylic acid such as trimellitic acid has been used as an acid monomer component thereof from the viewpoints of a good fusing ability and a good durability of the resulting toner. For example, Patent Document 1 discloses a toner obtained by using a polyester resin containing an aromatic dicarboxylic acid component such as isophthalic acid and terephthalic acid, an aromatic tricarboxylic acid component such as trimellitic acid or an aliphatic dicarboxylic acid component such as dodecenylsuccinic acid as a constitutional unit thereof.
In addition, as the method for producing the toner having a small particle size, there has been proposed, for example, a method for producing a toner for electrophotography containing a binder resin and a colorant which includes the step of forming the binder resin into fine particles having a volume-median particle size (D50) of from 0.05 to 3 μm in an aqueous medium in the presence of a nonionic surfactant at a temperature ranging from a temperature lower by 10° C. than a cloud point of the nonionic surfactant to a temperature higher by 10° C. than the cloud point (for example, refer to Patent Document 2).
Patent Document 1: JP 6-19204A
Patent Document 2: JP 2006-106679A